# This code is part of Qiskit.
#
# (C) Copyright IBM 2017, 2019.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.

"""Tests for the converters."""

import math
import unittest

import numpy as np

from qiskit.converters import circuit_to_instruction
from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
from qiskit.circuit import Qubit, Clbit, Instruction
from qiskit.circuit import Parameter
from qiskit.circuit.classical import expr, types
from qiskit.quantum_info import Operator
from qiskit.exceptions import QiskitError
from test import QiskitTestCase  # pylint: disable=wrong-import-order


class TestCircuitToInstruction(QiskitTestCase):
    """Test Circuit to Instruction."""

    def test_flatten_circuit_registers(self):
        """Check correct flattening"""
        qr1 = QuantumRegister(4, "qr1")
        qr2 = QuantumRegister(3, "qr2")
        qr3 = QuantumRegister(3, "qr3")
        cr1 = ClassicalRegister(4, "cr1")
        cr2 = ClassicalRegister(1, "cr2")
        circ = QuantumCircuit(qr1, qr2, qr3, cr1, cr2)
        circ.cx(qr1[1], qr2[2])
        circ.measure(qr3[0], cr2[0])

        inst = circuit_to_instruction(circ)
        q = QuantumRegister(10, "q")
        c = ClassicalRegister(5, "c")

        self.assertEqual(inst.definition[0].qubits, (q[1], q[6]))
        self.assertEqual(inst.definition[1].qubits, (q[7],))
        self.assertEqual(inst.definition[1].clbits, (c[4],))

    def test_flatten_registers_of_circuit_single_bit_cond(self):
        """Check correct mapping of registers gates conditioned on single classical bits."""
        qr1 = QuantumRegister(2, "qr1")
        qr2 = QuantumRegister(3, "qr2")
        cr1 = ClassicalRegister(3, "cr1")
        cr2 = ClassicalRegister(3, "cr2")
        circ = QuantumCircuit(qr1, qr2, cr1, cr2)
        circ.h(qr1[0]).c_if(cr1[1], True)
        circ.h(qr2[1]).c_if(cr2[0], False)
        circ.cx(qr1[1], qr2[2]).c_if(cr2[2], True)
        circ.measure(qr2[2], cr2[0])

        inst = circuit_to_instruction(circ)
        q = QuantumRegister(5, "q")
        c = ClassicalRegister(6, "c")

        self.assertEqual(inst.definition[0].qubits, (q[0],))
        self.assertEqual(inst.definition[1].qubits, (q[3],))
        self.assertEqual(inst.definition[2].qubits, (q[1], q[4]))

        self.assertEqual(inst.definition[0].operation.condition, (c[1], True))
        self.assertEqual(inst.definition[1].operation.condition, (c[3], False))
        self.assertEqual(inst.definition[2].operation.condition, (c[5], True))

    def test_flatten_circuit_registerless(self):
        """Test that the conversion works when the given circuit has bits that are not contained in
        any register."""
        qr1 = QuantumRegister(2)
        qubits = [Qubit(), Qubit(), Qubit()]
        qr2 = QuantumRegister(3)
        cr1 = ClassicalRegister(2)
        clbits = [Clbit(), Clbit(), Clbit()]
        cr2 = ClassicalRegister(3)
        circ = QuantumCircuit(qr1, qubits, qr2, cr1, clbits, cr2)
        circ.cx(3, 5)
        circ.measure(4, 4)

        inst = circuit_to_instruction(circ)
        self.assertEqual(inst.num_qubits, len(qr1) + len(qubits) + len(qr2))
        self.assertEqual(inst.num_clbits, len(cr1) + len(clbits) + len(cr2))
        inst_definition = inst.definition
        cx = inst_definition.data[0]
        measure = inst_definition.data[1]
        self.assertEqual(cx.qubits, (inst_definition.qubits[3], inst_definition.qubits[5]))
        self.assertEqual(cx.clbits, ())
        self.assertEqual(measure.qubits, (inst_definition.qubits[4],))
        self.assertEqual(measure.clbits, (inst_definition.clbits[4],))

    def test_flatten_circuit_overlapping_registers(self):
        """Test that the conversion works when the given circuit has bits that are contained in more
        than one register."""
        qubits = [Qubit() for _ in [None] * 10]
        qr1 = QuantumRegister(bits=qubits[:6])
        qr2 = QuantumRegister(bits=qubits[4:])
        clbits = [Clbit() for _ in [None] * 10]
        cr1 = ClassicalRegister(bits=clbits[:6])
        cr2 = ClassicalRegister(bits=clbits[4:])
        circ = QuantumCircuit(qubits, clbits, qr1, qr2, cr1, cr2)
        circ.cx(3, 5)
        circ.measure(4, 4)

        inst = circuit_to_instruction(circ)
        self.assertEqual(inst.num_qubits, len(qubits))
        self.assertEqual(inst.num_clbits, len(clbits))
        inst_definition = inst.definition
        cx = inst_definition.data[0]
        measure = inst_definition.data[1]
        self.assertEqual(cx.qubits, (inst_definition.qubits[3], inst_definition.qubits[5]))
        self.assertEqual(cx.clbits, ())
        self.assertEqual(measure.qubits, (inst_definition.qubits[4],))
        self.assertEqual(measure.clbits, (inst_definition.clbits[4],))

    def test_flatten_parameters(self):
        """Verify parameters from circuit are moved to instruction.params"""
        qr = QuantumRegister(3, "qr")
        qc = QuantumCircuit(qr)

        theta = Parameter("theta")
        phi = Parameter("phi")
        sum_ = theta + phi

        qc.rz(theta, qr[0])
        qc.rz(phi, qr[1])
        qc.u(theta, phi, 0, qr[2])
        qc.rz(sum_, qr[0])

        inst = circuit_to_instruction(qc)

        self.assertEqual(inst.params, [phi, theta])
        self.assertEqual(inst.definition[0].operation.params, [theta])
        self.assertEqual(inst.definition[1].operation.params, [phi])
        self.assertEqual(inst.definition[2].operation.params, [theta, phi, 0])
        self.assertEqual(str(inst.definition[3].operation.params[0]), "phi + theta")

    def test_underspecified_parameter_map_raises(self):
        """Verify we raise if not all circuit parameters are present in parameter_map."""
        qr = QuantumRegister(3, "qr")
        qc = QuantumCircuit(qr)

        theta = Parameter("theta")
        phi = Parameter("phi")
        sum_ = theta + phi

        gamma = Parameter("gamma")

        qc.rz(theta, qr[0])
        qc.rz(phi, qr[1])
        qc.u(theta, phi, 0, qr[2])
        qc.rz(sum_, qr[0])

        self.assertRaises(QiskitError, circuit_to_instruction, qc, {theta: gamma})

        # Raise if provided more parameters than present in the circuit
        delta = Parameter("delta")
        self.assertRaises(
            QiskitError, circuit_to_instruction, qc, {theta: gamma, phi: phi, delta: delta}
        )

    def test_parameter_map(self):
        """Verify alternate parameter specification"""
        qr = QuantumRegister(3, "qr")
        qc = QuantumCircuit(qr)

        theta = Parameter("theta")
        phi = Parameter("phi")
        sum_ = theta + phi

        gamma = Parameter("gamma")

        qc.rz(theta, qr[0])
        qc.rz(phi, qr[1])
        qc.u(theta, phi, 0, qr[2])
        qc.rz(sum_, qr[0])

        inst = circuit_to_instruction(qc, {theta: gamma, phi: phi})

        self.assertEqual(inst.params, [gamma, phi])
        self.assertEqual(inst.definition[0].operation.params, [gamma])
        self.assertEqual(inst.definition[1].operation.params, [phi])
        self.assertEqual(inst.definition[2].operation.params, [gamma, phi, 0])
        self.assertEqual(str(inst.definition[3].operation.params[0]), "gamma + phi")

    def test_registerless_classical_bits(self):
        """Test that conditions on registerless classical bits can be handled during the conversion.

        Regression test of gh-7394."""
        expected = QuantumCircuit([Qubit(), Clbit()])
        expected.h(0).c_if(expected.clbits[0], 0)
        test = circuit_to_instruction(expected)

        self.assertIsInstance(test, Instruction)
        self.assertIsInstance(test.definition, QuantumCircuit)

        self.assertEqual(len(test.definition.data), 1)
        test_instruction = test.definition.data[0]
        expected_instruction = expected.data[0]
        self.assertIs(type(test_instruction.operation), type(expected_instruction.operation))
        self.assertEqual(test_instruction.operation.condition, (test.definition.clbits[0], 0))

    def test_zero_operands(self):
        """Test that an instruction can be created, even if it has zero operands."""
        base = QuantumCircuit(global_phase=math.pi)
        instruction = base.to_instruction()
        self.assertEqual(instruction.num_qubits, 0)
        self.assertEqual(instruction.num_clbits, 0)
        self.assertEqual(instruction.definition, base)
        compound = QuantumCircuit(1)
        compound.append(instruction, [], [])
        np.testing.assert_allclose(-np.eye(2), Operator(compound), atol=1e-16)

    def test_forbids_captured_vars(self):
        """Instructions (here an analogue of functions) cannot close over outer scopes."""
        qc = QuantumCircuit(captures=[expr.Var.new("a", types.Bool())])
        with self.assertRaisesRegex(QiskitError, "Circuits that capture variables cannot"):
            qc.to_instruction()

    def test_forbids_input_vars(self):
        """This test can be relaxed when we have proper support for the behavior.

        This actually has a natural meaning; the input variables could become typed parameters.
        We don't have a formal structure for managing that yet, though, so it's forbidden until the
        library is ready for that."""
        qc = QuantumCircuit(inputs=[expr.Var.new("a", types.Bool())])
        with self.assertRaisesRegex(QiskitError, "Circuits with 'input' variables cannot"):
            qc.to_instruction()

    def test_forbids_declared_vars(self):
        """This test can be relaxed when we have proper support for the behavior.

        This has a very natural representation, which needs basically zero special handling, since
        the variables are necessarily entirely internal to the subroutine.  The reason it is
        starting off as forbidden is because we don't have a good way to support variable renaming
        during unrolling in transpilation, and we want the error to indicate an alternative at the
        point the conversion happens."""
        qc = QuantumCircuit()
        qc.add_var("a", False)
        with self.assertRaisesRegex(
            QiskitError,
            "Circuits with internal variables.*You may be able to use `QuantumCircuit.compose`",
        ):
            qc.to_instruction()


if __name__ == "__main__":
    unittest.main(verbosity=2)
